Signal system



April 3, 1928. 1,664,860

R. A; HElslNG sIGNALsYsTEM Filed may 1e. 1924 Patented Apr. 3, 1928.

UNITED STATES .PATENT orales.,

`nAYrroNn n. nnIsiNe, OFMILLBNBN, NEW JnnsnY, AssIGNon 'ro WESTERN ELEC- Tno COMPANY, Nc-Onronnrnn, on NEW YORK, N. Y., A CORPORATION or NEW YORK.

SIGNAL SYSTEM.

My invention relatesy broadly to signaling, and more particularly to a multiplex duplex transmission andl receiving system for radio communication.

One. of the objects ot my invention is to provide a multiplex system ot radio communication which may employ one'radiating structure or antenna for a plurality not duplex radio communicationsystems.

Another object o't my invention is to `provide circuit `arrangements in ay multiplex system in which -the several channels are provided,l with means for reducing Vinterference from `the local transmitting energy in the same channel or associated channels connected to the same antenna.l

Still anotherAo-bject of my invention is to provide a multiplex transmission systemv for operation on the same antenna having means connected in the several channels tor preventing or reducing reaction ot the separate transmitting channels upon each other while enabling etlicient radiation ot signalsfrom the same antenna without mutualinterterence.

Still-another object of vmy invention is to provide selective circuit arrangementsin the receiving channels of a two-way multiplex system eliminating undesired interference trom the transmitting energy in the same channel or from sources ot energy in adjacent channels, at the Same time usefully employing a -portion of the `transmitting energy at the sameV station for operation with incomingsignaling energyto produce oscillations of intermediate `Jfrequency differing from other beat frequency .oscillationswhich may occur in the system, which oscillations may lie-selected, detected, and caused to reproduce the incoming signals without interference from cross-tall; or from oscillations occurring simultaneously at other points in the system.

The invention will be more clearly understood by reference to the following specification and the accompanying drawings, in which:

lFig. 1 represents a circuit arrangement Ifor la multiplex transmitting circuit; and Fig. 2shows a circuit arrangement for a plurality of two-way multiplex channels operating in connection with the same antenna.

1924. Serial No. 713,694.

Heretofore in the art diliiculty has been experienced in the operation of radio transmission and receiving systems closely adjacent each other by reason of cross-talkdisturbances and mutualinterference by-reac. tion ofgene system upon .the other. In installations onshipboard it has been necesaA sary to provide separate antennae for eachl channel .ot communication and substantially separate the channels on vwidely -di'erent wave lengths, ^and even kin such installations it has been very ditiicultgtoavoid `reaction of one system upon fthe other. f

-In the present invention I provide a multiplex radio communication system in ywhich the several channels operate upon the same antenna system with means interposed :in each of the channels for reducing reaction ot one system upon t-he.otherenabling communications to ybe carried on rSimultaneously utilizing the same antenna system.

vReferring to Fig.'1 4ofthe drawings, a multiplex transmission system has .been shown in which several channels 1, 2, and 3 are connected to the same antenna-ground system 4indicated by yreference characters 4 and 5. yInductances 6, 7 and 8 are included in the antenna-ground circuit 4, 5` to which the several transmission channels 1, 2 and 3 vare inductively coupled.

The ytransmission channel indicated hy reference character 1 has .been ,illustrated diagrammatically as including agenerator of sustained oscillations O, a modulator M operated from a suitahlev modulation circuit represented by reference characters 19. and y10, and ;a power ampliiier `P for, increasing the amplitude of vthe Amodulated Vsignals iin-- pressed upon the tuned circuit 11, 12 connected in series with the inductive means 1 4 which `relates to transmission channel 1 to inductance 6 inthe antenna-ground system a, 5;

The transmission channels 2, and 3 'may contain substantially similar circuit .arrange-ments as described in connection with transmission channel 1. The .transmission channel 2 includes tuned circuit l5, '16 oonnected in series with the inductive means 17 which couples channel 2 with inductance? in the yantenna-ground system 4, A5. 'The channel 3 may include tuned circuit 18, 19 connected inseries with inductive -meansQO Which is coupled With inductance 8 in the antenna-ground circuit 4, 5.

The antenna circuit includes a plurality of branch circuits 21, 22 and n3. Circuit 21 including variable capacity 24 is Vtimed combination `with "the VAanteim"a-'ground circuit 4, 5 to the frequency of channel 3. The loop-resonant circuits 25 and 26, in branches Y 22 and 23V respectively, are each tuned to the mined by the constants of branch. 2l and.

the antenna-ground circuit. The branch 22 is tuned in combination with the branch 21 and the antenna-ground circuit to the fre quency of channel. 2. This tuning is effected by variable condenser' 27. The loop-resonant circuit 23 in brand-123 is tuned to the frequency of channel 2 and therefore effecH tively removes branch 23 with respect to that frequency in the manner above described With reference to loop-resonant circuits 25 and 26. The branch 23 is tuned in combination with branches 21 and 22 and the antenna-ground circuit to the frequency of channel 1. This is accomplished by variable condenser29. The antenna system accordingly is given 3 vdegrees of freedom corresponding -to the respective frequencies of the three transmitting channels.

Tn describing the tuning means for the various combinations, that is, the variable condensers 24, 27 and 29, it Was assumed that the frequencies of the three channels decreased from channel 3 to channel 1. lt is obvious that the allocation of the respective frequencies to the various combinations could be made otherwise by the use of inductances instead ofor in combination with said condensers. Tf both in'ductances and condensers are used, they be connected in series or in parallel. ln a similar manner, provision can be made for any desired number of channels. For example, for four channels, a fourth branch would be added, which would contain a loop-resonant circuit tuned to each of the other three frequencies and a means for tuning` the branch, in coinbination With the remaining branches and the antenna-ground circuit, to the fourth frequency. f

Tn order to prevent reaction of one trans mission channel upon another, l provide shunt paths in each of the transmission channels offering loW impedance to the frequencies produced by the other transmission channels. That is to say, in transmission channel 1 ll provide shunt paths 33 and including respectively inductance 35 shunted by capacity 36 in series With capacity 37 and an inductance 38 shunted by capacity 39 in series With capacity 40. Tn these paths Leeaeeo the tvvo loop-resonant circuits constituted by the elements 35, 36, 33 and 39 are each tuned to the frequency of channel 1.V The paths therefore offer high impedance to the frequency emitted by transmission channel 1. `The tivo `paths are tuned respectively to the frequencies of channels 2f and 3 by variable condensers 37 and 4G and therefore together oder low impedance to frequencies emitted by both of said channels, preventingy the passage of undesired currents into the transmitting apparatus connected with Atransmission channel 1.

The transmission channel 2 is provided Y Withr a shunt path 41 including variable capacities 42 and 43 and inductances 44 and 45. Tf it he assumed that the frequencies of channels-'1 and 3Yare equally spaced'from the frequency of channel 2 and the groups of elements 42, 45 and 43, 44 are tuned re spectively to the frequencies of channels l and 3 the loopaesonant circuit constituted by all four elements Will be tuned to the frequency of channel 2, accordingly path 41 has a high impedance to currents of the frequencv employed by channels 2 and a low:

impedance to undesired currents Which may have a tendency to react upon the channel 2 from channels 1 and 3. l

Transmission channel 3 is similar to channel 1, it contains shunt paths 46' and 47 in cluding in'ductance 43 shunted by capacity 49 in series with in'ductance 50 and capacity 51, and inductance 52 shunted by capacity 53 in series with inductance 54 and capacity 55 respectively, the said shunt paths offerH ing high impedance to the signaling frequencv in channel 3 but low impedance to interfering currents which may react upon channel 3 from channels 1 and 2.

2 shows the diagrammatic arrangei'nentof a plurality of duplex communication chaimels operating upon the same an` tenna system. Three channels have been shown at 61, 62 and 63, each including circuits for screening each channel against interference from adjacent channels While perxi mitting transmission and reception of energy in the particular channel in Which the screening means may be located. .The channel 61 is divided into a transmitting circuit 64 and a receiving circuit 65. The transmission system connected to the `transmission circuit 64 may include a source of sustained oscillations designated at C connected to impress .energy of constant frequency upon a modulation circuit including electron tube 66. The high frequency oscillations from the generator C may be modulated at voice frequencyfrom a circuit represented at 67 and the modulated high frequency oscillations impressed upon the amplification systemGS operating to increase theA amplitude of the transmitting energy and deliver the energy to the radiating antenna system compri-'sing antenna 56', induct-ance 69, capacity and ground 71. Circuits@ and b consisting of inductance 72 shunted by capacity 73, and inductance 74 shun-ted by capacity 75", are provided in the antenna connection for the purpose of screening the communication channel from reaction or disturbances of oscillations produced in adjacent channels as Will be hereinafter described. The receiving system of channel 61 includes a cir cuit consisting` of inductance 76 and shunt capacity 77, which is closely resonant to the frequency of the oscillator C of the transmitting circuit 6ay but can be detuned from that frequency sui'iiciently to permit a desired amount of energy from the local transmitting channel to flow in the receiving circuit. rihis energ r is used in cooperation with= the incoming signal Aenergy for the production of abeat note, enabling the signals to be observed. The receiving circuit 65 includes the primary antenna inductance 78 and tuningcondenser 79 connected to ground 80. The frequency derived from the interaction of the incoming signal energy with the energy from the local source of oscillations inay be impressed upon detector tube 81 and the resultant beat frequency again impressed upon a detector circuit including tube 82 to finally reproduce the signal transmitted from the distant station.

The second duplex channel represented by connection 62 With the antenna 56 has circuits a and c interposed between the transmitting and receiving apparatus and the antenna system. These circuits a and c includev inductanccs 81 and 82; shunted by condensers and 84E respectively the cire cuits operating to eliminate the'passaige of undesired disturbances or reactions: from .the associated channels into the transmitting or receiving apparatus ofA the channel 62. The transmitter for this channel is represented as havingl a source of sustained oscillations indicated, at B connected with suitable modulation and amplification circuits represented generally at 853 the transmitter beingfmodula-ted at voice frequencies through circuit 86:. The transmitting energy is dclfivered to the antenna system through in-V ductance 87 connected in the antenna and groundcircuit in series With condenser 86. In the lead from the antenna 56 through connection 62 to the receiving apparatus in this channel there is interposed a: circuit including an inductance 89 shunted by condenser 901 tuned to exclude the frequency of the local source of oscillations B in its associated transmitter circuit. The received energy is impressed upon the receiving circuitthrough primary inductance 91 shunted by tuning condenser 92. A local source of oscillations may be supplied by means of'a local generator 93 coupled Withthe secondary Winding 9d through an inductance; 95.

An electron tube 95 is: connected to function as a'detector toI reduce the incoming signals to a beat netey at an intermediate frequency determined bythe frequency of the source 93 capable of beingeiiiciently' arnplified through amplifier 96 and selectively impressed upon another detector circuit in# c'luding-tube 97 through aser-ies of selective. circuits 98 delivering the received energy to operate a suitable responsive device indicated 99. The frequency kof source 93' is fixed by the desired intermediate frequencyr which should be different from that resulting from combii-iation of the incoming fiequency with the locally transmitted and other interfering frequencies.

Channel 63 is connected With the antenna 56. with circuits c and Z) interposed therein yfor excluding interference from the associated channels. The circuitsk 0 and conr- Cil prise inductances 100 and 101 shunted'by condenser-s 102 and 103 respectively, serving to exclude reactions from thelocal sou-'rees of oscillationl in the transmitter circuits of the closely adjacent channel-s. The transmitter in channel 63 may be provided with a local generator of oscillations designated as having a frequency A, the energyv lfrom Which modulated by signal in the manner described with reference to transmitting channel 6st is impressedon'the antennaI circuit to inductance 104i. The receiving systeni for the channel 63" includes a circuit in series therewith comprising inductance 105v and condenser 106 functioning to exclude undesired interference in the receiving system from the locally generated oscillations in the transmitter circuit. It may function as in channel 61 to permit-a desiredamount of the locally transmitted energy to flow to the receiving circuit. `The. receiver may be coupled to the system by primary Winding 107 and secondary Winding 108.

It Will be observed that means` are provided in each of the several channels. for suppressing reactions and interference from currents occurring simultaneously in the other channels. That is to say, circuits a and I) in channel 61 Willv suppress undesired oscillations or currents which. might be impressed upon channel 61y by channel 62 or 63. The circuit 76, 77 in the receiving portion of channel 61 suppresses from the receiving circuit all except a desired amount of energy derived fromthe local oscillator C of the transmitter in the same channel which may be utilized in reception. In channel 62 the circuits e and c suppress undesired currents which may be developed by channel 61 0F63. The circuit 839, 90v in channel 62 prevents undesired reaction. ofl the sustained Wave from generator B of the transmitter portion of the channel froml impressing itself upon the receiving portion of the channel. In channel 63 thecircuits-.aand Z. suprit ieu

ISO

press undesired currents'occurring in channels 61 and 62 While the circuit 105 and 106 in the receiving portion of the channel operates to prevent undesired reaction of the sustained Wave of generator A of the adjacent transmitter. All of these channels may therefore function in duplex operation in multiplex signaling on the same antenna 56 Without mutual reaction or cross-talk.

The incoming signaling energy in the antenna system 56 distributes to the several receiving channels Without interference, these being respectively selective to their individual message Waves as explained in the case of Fig. 1. For the purpose of clearly explaining the operation of the system, the

transmitting frequency in duplex channel 61 may be assumed to have a value equal to f1. The incoming signaling energy in antenna 56 selected by channel 61 may have a A portion of the transmitting frequency f1 being effectively utilized in the receiving portion of channel 61 as a local source of oscillations reacts with the frequency f2 from which is derived a beat note of a frequency f1*f2=f3 Which is rectified and observed. In like manner channel 62 may have a local source of transmitting energy of a frequency ff, and the incoming signaling energy in antenna 56 for this channel may be fzl. If desired, the frequency fll may not be used as a local source in the receiving channel but instead a local generator of a frequency 711 may be employed. The beat frequency thus derived Will be fil-fzlzfal which may be further rectified to enable the signals to be observed.

v Similarly the channel 63 may have a transmitting portion of frequency f1 and the incoming frequency in antenna 56 for this channel may be 7211. A portion of the transmitting frequency f1 may be utilized as a local source so that the beat frequency for the receiver Will be Y f111 f211:fs11

The beat frequency f3 may be further detected and the signal indicated.

l/Vhile I have described the invention in certain particular embodiments, I desire that it be understood that modifications may be made and I intend no limitationsupon the invention other than are imposed by the scope of the appended claims.

l/Vhat I claim is:

1. A transmitting channel comprising a transmitting conductor, a circuit associated in energy transfer relation thereto, and a reactive circuit in shunt to said circuit, said reactive circuit comprising a combination of impedance elements Which is loop-resonant at a frequency to be transmitted, and said reactive circuit, as measured between its terfrequency f2.

minals connected to said rst mentioned cir cuit, being also resonant at at leastl one frequency to be excluded.

2. A transmitting channel comprising a transmitting conductor, a circuit associated in energy transfer relation thereto, andv a reactive circuit in shunt to said circuit, said reactive circuit comprising a combination of impedance elements Which vis loop-resonant at a frequency to be transmitted, and said reactive circuit, as measured between its terminals connected to said first mentioned circuit, being series-resonant at a plurality lof frequencies to Vbe excluded.

3. A multituned antenna system compris- Y ing, in combination, a grounded aerial and a plurality of grounded circuits, corresponding to the numberV of frequencies tovwhich it is desired to tune the system as a Whole, connected in parallell With each other and with said grounded aerial portion; means in one parallel circuit Which combines with said grounded aerial portion to tune the sys,- tem to one desired frequency, anti-resonant means in each of the other parallel circuits to effectively isolate them from the grounded portion and the first parallel circuit at said other desired frequencies, means in a second parallel circuit Which combines With the grounded.` aerial portion and the first parallel circuit to tune the system to a second desired frequency, anti-resonant means in each of the parallel circuits, exclusive of the first and second, to effectively isolate them from the grounded aerial portion and the first and second parallel circuits, as to the first and second desiredl frequencies; and similarly for each of the other desired frequencies. Y

4:. A multiplex radio transmitting circuit comprising a plurality of sources of transJ mitting Waves of respectively dilerent frequency, individual transmission circuits associated With each source', each such circuit having connected across it as many shunt circuits as there are other transmitting cir cuits, eachshunt circuit being tuned to be anti-resonant at the frequency of the Waves from the source connected to that transmission circuit, each of said shunt circuits being series resonant at the frequency of a different respective one of the-other Wave sources, and an antenna connected in common to all of said transmitting circuits and having a plurality of degrees of freedom corresponding in frequency to they individual frequencies of each of said transmission circuits.

5. A system as defined in claim 4in Which each of said transmission circuits includes means for making the circuit series resonant at the frequency of the Waves transmitted b it.

y6.r A multi-tuned antenna system compris-V ing, in combination, a grounded aerial and a plurality of grounded branches, means to branches for effectively isolating it from tune the grounded aerial circuit to one of said aerial circuit at said second operating the operating frequencies, anti-resonant cirfrequency, and means in said last-mentioned cuits in each of a plurality of said branches branch Which combines with the grounded 5 for effectively isolating them from said aerial portion and the other branch to tune l5 aerial circuit at said operating frequency, the system to a third operating frequency.

means in one of said branches which com* In Witness whereof, I hereunto subscribe bines with said first tuning means to tune my name this 15th day of May A. D., 1924.

the system to a second operating frequency, 10 an anti-resonant circuit in another of said RAYMOND A. HEISING. 

